Bunuel
A cylindrical pitcher with a radius 5 is filled with beer to a height of 9 inches. If the beer is poured from the first pitcher to a second pitcher with no spillage and fills the second pitcher to a height of 4 inches, what is the radius of the second pitcher?
A. 15 inches
B. 12.5 inches
C. 9 inches
D. 8 inches
E. 7.5 inches
The volume of beer is equal in both pitchers.
Volume of [the liquid in] a cylinder, and thus in the first pitcher:
\(V =\pi r^2 h\)
\(V=\pi* 5^2*9=225\pi\)
That volume of beer is in the second pitcher. Solve for radius. Second pitcher:
\(225\pi=\pi r^2h=\pi* r^2* 4\)
\(\frac{225}{4}=r^2\)
\(56.25=r^2\)
\(\sqrt{56.25}=r\)
Between which two perfect squares does \(56.25\) lie?
\(7^2=49 < 56.25 < 64=8^2\)
The radius is between \(7\) and \(8\).
Answer E
Alternatively,
check the answer choices.(C) \(9^2=81\) -> too great. We need 56.25
(D) \(8^2=64\) -> too great.
By POE, (E) is the answer.
And: (E) 7.5 is between 7 and 8
\(7^2 = 49\)
\(8^2=64\)
\(49<56.25<64\) - That works.
Answer E